Method of manufacturing a wood-based board and such a wood-based board

ABSTRACT

A method of manufacturing a wood-based board. The method includes applying at least one first fibre mat including a first mix comprising lignocellulosic particles and a binder on a carrier, applying a second fibre mat including a second mix including cellulosic particles and a binder on said at least one first fibre mat, and pressing said at least one first fibre mat into a base layer and the second fibre mat into a surface layer simultaneously, thereby forming a wood-based board. Also, to such a wood-based board.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/742,963, filed on Jan. 15, 2020, now U.S. Pat. No. 11,084,191, whichis a continuation of U.S. application Ser. No. 14/305,251, filed on Jun.16, 2014, now U.S. Pat. No. 10,659,452, which claims the benefit ofSwedish Application No. 13507330, filed on Jun. 17, 2013. The entirecontents of each of U.S. application Ser. No. 16/742,963, U.S.application Ser. No. 14/305,251 and Swedish Application No. 13507330 arehereby incorporated herein by reference in their entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate to a method ofmanufacturing a printable wood-based board, such as a MDF, HDF, OSB orparticle board, and such a printable wood-based board.

TECHNICAL BACKGROUND

Conventional Medium Density Fibre boards (MDF), High Density Fibreboards (HDF) and particle boards generally have a brown colour, whichmay vary with the type of wood raw material used. MDF and HDF are oftenused as a core material to which a veneer or laminate such as DPL(Direct Pressure Laminate) or HPL (High Pressure Laminate) is adhered.An alternative to attaching a laminate is to print directly on a HDF orMDF in order to reduce cost. However, the colour of the MDF or HDF makesit difficult to print pale decors since the colour of the MDF or HDFshines through the printed décor. Accordingly, it is difficult to printa paler colour than the colour of the HDF or MDF. Furthermore, acomparable large amount of ink may be required to obtain the desireddécor due to the underlying colour of the HDF or MDF, which increasesthe cost of the décor.

It is known from US 2007/0256804 to produce a white wood-based board ofbleached wood fibres and/or combined with beater dyeing with a whitepigment. However, using bleached wood fibres and pigment result in aboard produced to a considerable higher cost compared to a conventionalMDF or HDF.

GB 984,170 describes an improved chipboard, which may have a whitesurface comprising wood flour and titanium dioxide. The white surface isobtained by a large amount of titanium dioxide.

EP 1,250,995 discloses a method of extruding a thermoplastic compositematerial containing a thermoplastic resin and a vegetable filler.

SUMMARY

It is an object of at least certain embodiments of the presentdisclosure to provide an improvement over the above described techniquesand known art.

A further object of at least certain embodiments is to provide awood-based board having a pale to white or coloured surface.

A further object of at least certain embodiments is to provide awood-based board, which is suitable for being printed directly upon.

A further object of at least certain embodiments is to provide awood-based board having a printable surface at a low cost.

A further object of at least certain embodiments is to provide awood-based board on which pale or bright decors may be printed directlyupon.

At least some of these and other objects and advantages that will beapparent from the description have been achieved by a method ofmanufacturing a wood-based board according to a first aspect of thedisclosure. The method comprises applying at least one first fibre matcomprising a first mix comprising lignocellulosic particles and a firstbinder on a carrier, applying a second fibre mat comprising a second mixcomprising cellulosic particles and a second binder on said at least onefirst fibre mat, and pressing said at least one first fibre mat into alayer and the second fibre mat into a surface layer simultaneously,thereby forming a wood-based board.

The surface layer may be a top layer of the wood-based board.

Pressing preferably comprises applying heat and pressure. Pressing maycomprise curing the first and second binder of the first and secondfibre mat, respectively.

The second fibre mat is applied on said at least one first fibre matprior to pressing said at least one first fibre mat, or at least priorto final pressing. In one embodiment, the second fibre mat is applied onsaid at least one first fibre mat prior to curing said at least onefirst fibre mat.

By lignocellulosic particles are meant particles comprising celluloseand/or hemicellulose and lignin. The particles may be wood fibres orvegetable fibres such as jute, linen, flax, hemp, bamboo, bagasse andsisal.

By cellulosic particles are meant particles comprising no orsubstantially no lignin (e.g., less than 5% lignin). The particles maybe produced from wood, preferably wood fibres or vegetable fibres suchas cotton.

In one embodiment, the surface layer comprises no pigment. The surfacelayer may be free from pigments. The surface layer may consist ofcellulosic particles, a binder and, optionally, additives selected fromhydrophobing agents, hardener, and catalysts.

An advantage of embodiments of the present disclosure is that awood-based board having a pale to white surface is obtained. Thereby,the wood-based board is suitable for being directly printed on. Thewood-based board is thereby also suitable for being used as a core for asurface layer being at least partly translucent. The wood-based boardmay also be used without any further treatment.

As a result of the pale to white colour of the surface layer of thewood-based board, a high quality print may be printed directly on thesurface of the wood-based board. Especially, pale colours may be printedon the wood-based board. The disadvantages of printing on a conventionalwood-based board having a brown colour are overcome or at least reduced.

Furthermore, by using cellulosic particles in the surface layer, a paleto white surface of the wood-based board may be achieved at a lower costcompared to when using pigment, such as titanium dioxide, to obtain awhite surface. The amount of pigment, such as titanium dioxide, can bereduced or eliminated.

Another advantage is that by using cellulosic particles only in thesurface layer, a pale to white surface of the wood-based board may beachieved at a lower cost compared to producing a wood-based board ofentirely cellulosic particles. The cellulosic particles may be only usedwhere required, i.e., at a surface.

By arranging a pale to white surface layer, the need for covering thewood-based board with a paper or similar in order to reduce thevisibility of the core is eliminated, or at least reduced.

By printing directly on the surface of the wood-based board, and sinceno paper is required to cover the surface of the board, the number ofrequired steps in the manufacturing process is reduced. The cost forproducing a wood-based board having for example a printed decorativedesign is reduced.

The step of pressing, which may include curing, may comprisesimultaneously adhering said base layer and the surface layer to eachother. Curing may take place by applying heat and pressure to said baselayer and/or the surface layer. Thereby, the wood-based board is formedin one step.

The step of pressing, which may include curing, said at least one fibremat and the second fibre mat may comprise applying heat and pressure,and wherein pressure and/or binder content of the second fibre mat arechosen such that the surface layer remains opaque after curing. Thereby,the base layer remains invisible through the surface layer after curing.The base layer does not shine through the surface layer after curing. Ifthe pressure applied exceeds a certain limit, there is a risk that thesurface layer becomes transparent such that the colour of the underlyingbase layer shines through the surface layer. By adapting the pressureapplied to the binder content of the surface layer such that the surfacelayer still contains air pockets after curing, the surface layer mayremain opaque after curing. For example, the surface layer preferablyhas an opacity of at least 80%.

The step of pressing may comprise curing said at least one first fibremat into a base layer and the second fibre mat into a surface layersimultaneously.

The method may further comprise printing, preferably by digital printingor rotogravure printing, a print on the surface layer after pressing,which may involve curing. Printing may be performed directly on thesurface layer of the wood-based board, without any intervening layers.In one embodiment, a primer may be applied on the surface layer beforeprinting. The primer may comprise pigments such as titanium dioxide.

The method may further comprise printing, preferably by digitalprinting, a print on the second fibre mat before pressing. A protectivelayer may be applied on the print before pressing. Thereafter, alllayers are pressed together in one step. By providing cellulosicparticles in the surface layer, it is possible to print in the surfacelayer prior to pressing. Since the cellulosic particles are relativelysmall, void space between the particles is at least reduced, therebyreducing ink drops from permeating into the layer and being displacedduring pressing.

Pigment or pigments may be included in the second mix, for example toform a coloured surface layer or such that the pigments are chosen tomatch the print. For example, it may be desirable to have a slightlygrey colour of the print layer. This may be achieved by adding pigmentsand/or by using a certain amount of recycled fibres.

The carrier may be a conveyor belt, or any other type of conveyordevice.

The method may further comprise applying a protective layer on thesurface layer. The protective layer may be an overlay sheet, a lacquerlayer, a powder overlay comprising wood particles and a binder. Theprotective layer may be a radiation curing layer such that a UV curinglayer. The protective layer may be applied prior or after pressing.

The cellulosic particles of the second mix may be at least partiallybleached. By using at least partly bleached particles such as at leastpartly bleached fibres, the lignin content of the fibres is furtherreduced.

The lignocellulosic particles of the first mix may be refined woodfibres, wood chips, unrefined wood fibres, wood strands, or sawdust.Depending on the type of lignocellulosic fibres used, the wood-basedboard obtain properties similar to a MDF, HDF, particle board, OSB etc.

The first binder of the first mix may be a thermosetting resin. Thethermosetting binder may be an amino resin. The thermosetting binder maybe melamine formaldehyde resin, urea formaldehyde resin, or acombination thereof, or a co-condensation thereof such as MUF (melamineurea formaldehyde). The binder may be an isocyanate resin.

The second binder of the second mix may be a thermosetting resin. Thethermosetting binder may be an amino resin. The thermosetting binder maybe melamine formaldehyde resin, urea formaldehyde resin, or acombination thereof, or a co-condensation thereof such as MUF (melamineurea formaldehyde). The binder may be an isocyanate resin.

The wood-based board may be a MDF or HDF. If using refined wood fibres,the resulting wood-based board corresponds to a MDF or HDF.

The wood-based board may be a particle board or an OSB. If using woodchips, the resulting wood-based board corresponds to a particle board.

The lignocellulosic material of the first mix may have similarproperties as the cellulosic properties of the first mix regardingbinder content, humidity etc. The particle size of the lignocellulosicmaterial of the first mix may essentially correspond to the particlesize of the cellulosic material of the second mix.

The base layer may comprise a lower base layer and an upper base layer,wherein the particle size of the lignocellulosic particles of the lowerbase layer is less than the particle size of the lignocellulosicparticles of the upper base layer. By using larger particle size of thelignocellulosic particles of the upper base layer, i.e. the layerarranged between the lower base layer and the surface layer, thethickness of the wood-based board may be increased without increasingthe weight of the board to the same extent by incorporating air in theupper base layer.

The lignocellulosic material of the lower base layer may have similarproperties as the cellulosic properties of the surface layer regardingbinder content, humidity etc. The particle size of the lignocellulosicmaterial of the first mix may essentially correspond to the particlesize of the cellulosic material of the second mix.

According to a second aspect of the disclosure, a wood-based board isprovided. The wood-based board comprises a base layer comprisinglignocellulosic particles and a first binder, a surface layer comprisingcellulosic particles and a second binder, and wherein the building panelcomprises a portion wherein cellulosic particles from the surface layerare mixed with lignocellulosic particles from said base layer.

Embodiments of the second aspect of the disclosure may incorporate allthe advantages previously discussed, whereby the previous discussion isapplicable also for the wood-based board.

The wood-based board may be a HDF or MDF. Alternatively, the wood-basedboard may be a particle board or an OSB.

The first binder may be a thermosetting binder, for example, an aminoresin.

The second binder may be a thermosetting binder, for example, an aminoresin.

The wood-based board may be produced according to the first aspect ofthe disclosure.

According to a third aspect of the disclosure, a method of manufacturinga wood-based board is provided. The method comprises: applying at leastone first fibre mat comprising a first mix comprising lignocellulosicparticles and a first binder on a carrier, applying a surface layercomprising cellulosic particles on said at least one first fibre matprior to pressing said at least one fibre mat, and pressing the surfacelayer to said at least one first fibre mat, thereby adhering the surfacelayer to said at least one first fibre mat and forming a wood-basedboard.

Preferably, pressing comprises applying heat and pressure.

An advantage of embodiments of the present disclosure is that awood-based board having a pale to white surface is obtained, and forexample having a white grade measured according to Berger of more than80. Thereby, the wood-based board is suitable for being directly printedon. The wood-based board is thereby also suitable for being used as acore for an additional surface layer being at least partly translucent.The wood-based board may also be used without any further treatment. Thedisadvantages of printing on a conventional wood-based board having abrown colour are overcome or at least reduced by arranging a surfacelayer comprising cellulosic fibres on the first fibre mat.

Another advantage is that by arranging a surface layer comprisingcellulosic particles, a pale to white surface of the wood-based boardmay be achieved at a lower cost compared to producing a wood-based boardof cellulosic particles, or by incorporating pigments in the mix inorder to obtain a white surfaces. The cellulosic particles may be onlyused where required, i.e. at the surface.

Furthermore, the surface layer is attached to the fibre mat in the samestep as the fibre mat is pressed into a board. Thereby, no additionalstep is required to provide the board with a surface layer suitable forbeing printed on.

The surface layer may comprise a sheet comprising cellulose particles,preferably a paper sheet.

The sheet may be impregnated or unimpregnated. The binder of the firstfibre mat may instead impregnate the sheet during pressing. Ifimpregnated, the sheet may be impregnated with a thermosetting bindersuch as an amino resin.

The sheet may be pigmented. The sheet may, for example, be a whitepaper.

The step of pressing may comprise curing said at least one first fibremat into a base layer. Preferably, the surface layer is applied on thefirst fibre mat prior to curing said at least one first fibre mat.

The method may further comprise printing, preferably by digitalprinting, a print on the surface layer prior or after pressing.

The carrier may be a conveyor belt.

The first binder may be a thermosetting binder, for example an aminoresin. The method may comprise curing the first binder during pressing.

As described above in relation to the first aspect of the disclosure,the surface layer may in one embodiment comprise cellulosic fibres and asecond binder applied as first fibre mat.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will by way of example be described in moredetail with reference to the appended schematic drawings, which showembodiments of the present disclosure.

FIG. 1 shows a schematic representation of a method for forming awood-based board.

FIG. 2 a shows an embodiment of a wood-based board.

FIG. 2 b shows an embodiment of a wood-based board.

FIG. 2 c shows an embodiment of a wood-based board.

DETAILED DESCRIPTION

FIG. 1 shows a schematic representation of an equipment 1 and method forforming a wood-based board.

The equipment 1 comprises at least two mixing containers 2, 3. In afirst mixing container 2, lignocellulosic particles are provided. Thelignocellulosic particles comprise lignin. The lignocellulosic particlesmay be refined wood fibres.

In an embodiment wherein a HDF or MDF is formed, the refined wood fibresmay have a length of 0.5-20 mm, preferably 1-10 mm, and a width of0.01-2 mm, preferably 0.1-1 mm.

In another embodiment wherein a particle board is formed, thelignocellulosic particles are wood chips. A coarse fraction of the woodchips may have a length of 12-20 mm, a width about 4 mm, and thicknessabout 0.2-0.3 mm. A fine fraction of the wood chips may have a lengthless than 10 mm, a width about 1-2 mm, and a thickness about 0.1-0.2 mm.A thickness/length ratio for both the fine and the coarse fraction ofthe wood chips may be 1:100.

In another embodiment wherein an OSB (Oriented Strand Board) is formed,the lignocellulosic particles are wood chips. The wood chips may have alength of about 100 mm, a width about 10-20 mm, and thickness less than1 mm.

The lignocellulosic particles are mixed with a first binder in the firstmixing container 2 to form a first mix. The first binder may be athermosetting resin, preferably an amino resin. The first binder may bemelamine formaldehyde resin, urea formaldehyde resin, phenolformaldehyde resin, or a mix or combination thereof, or aco-condensation thereof such as MUF (melamine urea formaldehyde).Alternatively, the binder may be an isocyanate resin such as PMDI(polymeric methylene diphenyl diisocyanate) or EMDI (emulsifiablemethylene diphenyl diisocyanate). Preferably, the lignocellulosicmaterial is mixed with the first binder in a dry state.

In a second mixing container 3, cellulosic particles are provided. Thecellulosic particles may be at least partly bleached particles,preferably at least partly bleached wood fibres. The cellulosicparticles comprise no lignin, or substantially no lignin. The cellulosicparticles may have length of about 50-3000 μm, preferably about 150 μm.The cellulosic particles may have a width of 0.01-2 mm, preferably 0.1-1mm.

The cellulosic particles are mixed with a second binder in the secondmixing container 3 to form a second mix. The second binder may be athermosetting resin, preferably an amino resin. The second binder may bemelamine formaldehyde resin, urea formaldehyde resin, or a mix orcombination thereof, or a co-condensation thereof such as MUF (melamineurea formaldehyde). Alternatively, the second binder may be anisocyanate resin such as PMDI (polymeric methylene diphenyldiisocyanate) or EMDI (emulsifiable methylene diphenyl diisocyanate).Preferably, the cellulosic particles are mixed with the binder in a drystate.

Additives, such as catalysts, hydrophobic agents, etc., may be addedboth to the lignocellulosic particles and to the cellulosic particles.The additives are preferably added to the binder and added to thelignocellulosic and/or cellulosic particles when adding the binder.

The first mix comprising the lignocellulosic particles mixed with thefirst binder is thereafter fed to a first collecting container 4. Thesecond mix comprising the cellulosic particles mixed with the secondbinder is fed to a second collecting container 5.

The first mix comprising the lignocellulosic particles is thereafter fedto a first scattering device 6. The first scattering device 6 applies,preferably scatters, the first mix on a carrier 13. The carrier 13 maybe a conveyor belt. The first mix forms a first fibre mat 11 adapted toform a base layer 14 comprising lignocellulosic particles.

The second mix comprising the cellulosic particles mixed with the secondbinder is fed to a second scattering device 7. The second scatteringdevice 7 applies, preferably scatters, the second mix on the first fibremat 11 formed by the first mix. The second mix comprising the cellulosicparticles forms a second fibre mat 12 adapted to form a surface layer 15comprising cellulosic particles.

Both the first and/or the second mix may be applied as several layers,such that more than one layer forms the first fibre mat 11, and morethan one layer forms the second fibre mat 12.

The first fibre mat 11 adapted to form the base layer 14 and the secondfibre mat 12 adapted to form the surface layer 15 are thereafterconveyed to a pre-pressing station 8. The first fibre mat 11 and thesecond fibre mat 12 are pre-pressed, preferably without applying heat(cold pressing).

The first fibre mat 11 may also be pre-pressed before the second fibremat 12 is applied. As a further alternative, no pre-pressing may takeplace. However, the second fibre mat is applied to the first fibre matbefore final pressing of the first fibre mat. In one embodiment, thesecond fibre mat is applied to the first fibre mat prior to substantialcuring the first fibre mat.

After pre-pressing, the first fibre mat 11 adapted to form the baselayer 14 and the second fibre mat 12 adapted to form the surface layer15 are conveyed to a pressing station 9. The first fibre mat 11 and thesecond fibre mat 12 are pressed by applying heat and pressure.

In one embodiment, as an example for a continuous press, the temperaturemay be 180-240° C. Pressure may be applied for 3-10 seconds per mmproduct thickness. The pressure applied may be varying during the presscycle. Initially, a pressure of about 40 bars may be applied. Thepressure is thereafter lowered to about 5 bars. The pressure may beincreased towards the end of the press cycle to about 10-15 bars inorder to adjust the thickness of the board.

By applying heat and pressure, the first fibre mat 11 and the secondfibre mat 12 are pressed simultaneously into a base layer 14 and asurface layer 15, respectively. In one embodiment, the binder of thefirst and second fibre mat is cured by the pressing step.Simultaneously, the base layer 14 and the surface layer 15 adhere toeach other such that a wood-based board 10 is formed.

In one embodiment, no pre-pressing takes place and the first fibre mat11 and the second fibre mat 12 are directly conveyed to the pressingstation 9.

It is also contemplated that more than one first fibre mat may beapplied on the carrier to form more than one base layer.

As shown in FIG. 2 a , the wood-based board 10 thereby formed comprisesa base layer 14 comprising lignocellulosic particles and a surface layer15 comprising cellulosic particles. Depending on the type of particlesused for the base layer 14, the wood-based board may be a HDF, MDF,particle board, OSB etc. If the lignocellulosic particles are refinedfibres, the wood-based board forms a MDF or HDF. If the lignocellulosicparticles are wood chips, the wood-based board forms a particle board.Common for all embodiments is that the cellulosic particles of thesurface layer 15 forms a surface layer of the wood-based board 10. Thesurface layer 15 may have a pale to white colour.

Since the first fibre mat 11 and the second fibre mat 12 are pressedsimultaneously to form the base layer 14 and the surface layer 15, andsimultaneously adhered to each other, a portion wherein cellulosicparticles form the surface layer 15 are mixed with lignocellulosicparticles from the base layer 14 is formed.

About 200 g/m² or more of the second mix may be applied for forming thesurface layer 15.

In FIG. 2 b , a wood-based board 10′ comprises a lower base layer 14 acomprising lignocellulosic particles, an upper base layer 14 bcomprising lignocellulosic particles, and a surface layer 15 comprisingcellulosic particles. The lignocellulosic particles of the lower andupper base layer 14 a, 14 b may be wood chips. The wood-based board 10′may thus be a particle board having an integrated surface layer ofcellulosic particles.

Since the two first fibre mats and the second fibre mat 12 are pressedsimultaneously to form the lower base layer 14 a, the upper base layer14 b and the surface layer 15, and simultaneously adhered to each other,a portion wherein cellulosic particles form the surface layer 15 aremixed with lignocellulosic particles from the upper base layer 14 b isformed.

The lower base layer 14 a and the surface layer 15 may have similarproperties concerning dimensional stability and resistance to moisture.

The particle size of the lignocellulosic particles of the lower baselayer 14 a and of the upper base layer 14 b, respectively, may differ.In one embodiment, the particle size of the lower base layer 14 acorresponds to the particle size of the cellulosic particles of thesurface layer 15. The particle of the lower base layer 14 a and of thesurface layer 15 may have a length less than 10 mm, a width about 1-2mm, and a thickness about 0.1-0.2 mm. The upper base layer 14 b,arranged between the lower base layer 14 a and the surface layer 15, mayhave a particle size exceeding the particle size of the lower base layer14 a. In case of a particle board, the upper base layer 14 b maycomprise coarse wood chips having a length of 12-20 mm, a width about 4mm, and thickness about 0.2-0.3 mm. Thereby, a three layer wood-basedboard 10′ is obtained, for example a three layer particle board.

In one embodiment of a wood based board 10″, which is shown in FIG. 2 c, the second fibre mat 12 is replaced by a surface layer 15′ comprisingcellulosic particles, preferably comprising a sheet such as a papersheet. A first fibre mat 11 is applied on a carrier 13 as describedabove with reference to FIG. 1 . Instead of applying a second fibre mat12, a surface layer 15′ is applied on the first fibre mat 11. Thesurface layer 15′ may comprise a sheet comprising cellulosic particles,such as a paper sheet. The paper sheet may be an impregnated or anunimpregnated paper sheet. If impregnated, the sheet may comprise athermosetting binder such as an amino resin. When pressing the papersheet on the first fibre mat 12 comprising the first binder, the firstbinder may impregnate the surface layer 15′ simultaneously as adheringthe surface layer to the first fibre mat 11. The sheet may be printedprior or after being pressed to the first fibre mat 11. The sheet may bepigmented such as a white paper.

The wood-based board 10, 10′, 10″ as described above may be cut or sawnto a desired shape and size. The surface layer 15, 15′ of the wood-basedboard 10, 10′, 10″ may be ground. The surface layer 15, 15′ may besubjected to corona treatment. The wood-based board 10, 10′, 10″ may beused without any further surface layer or decorative print as awood-based board 10, 10′, 10″ having a pale to white surface.Alternatively, a décor layer may be attached to the wood-based board 10,10′, 10″. Due to the surface layer of cellulosic particles, a thinand/or pale décor layer may be used without any risk that the colour ofthe wood-based board 10, 10′, 10″ shines through the décor layer.

A print may be printed directly on the surface 15, 15′ of the wood-basedboard 10, 10′, 10″ of the above described type. The surface layer 15,15′ of cellulosic particles forms a print layer integrated in thewood-based board 10, 10′, 10″. The print is preferably applied by meansof digital printing. The digital printing device may comprise aDrop-on-Demand (DOD) inkjet printer, preferably a piezoelectric DODinkjet printer. Preferably, the ink is an aqueous ink, but solvent basedand UV curing inks may also be used. A print may also be applied byother suitable means such as rotogravure. A print may also be applied bydry particles used as colorants to create a digital image as describedin IPCOM000224950D published Jan. 15, 2013 at ip.com.

The print may be printed prior or after pressing of the first and secondfibre mats 11, 12. In one embodiment, the print is printed into thesecond fibre mat 12 prior to pressing. However, the second fibre mat 12may be pre-pressed prior to pressing. The printed second fibre mat 12 isthereafter pressed. In another embodiment, the print is printed on thesurface layer 15, 15′ after pressing, and preferably after curing.

The print may be a decorative design or a fantasy pattern. Thedecorative design may be natural designs and patterns such as a woodpattern or stone patterns.

The second mix forming the surface layer 15 may comprise pigment orpigments such that a coloured surface layer 15 is obtained. Thereby, awood-based board 10, 10′ having a coloured surface layer 15 is obtained.The wood-based board 10, 10′ can be used without any additional paintlayers and/or décor foils. A coloured surface layer 15 can be combinedwith a print as described above.

A protective layer or coating (not shown) may be applied on the surface15, 15′ of the wood-based board 10, 10′, 10″ according to any embodimentdescribed above. The protective coating may be applied on a decorativeprint printed on the surface 15 of the wood-based board 10, 10′, 10″.The protective coating may be an overlay paper such as a resinimpregnated paper, preferably comprising wear resistant particles suchas aluminium oxide particles, for example, corundum. The protectivecoating may be a powder overlay comprising a binder in powder form andpreferably cellulosic particles and wear resistant particles such asaluminium oxide particles, for example, corundum. The protective coatingmay be a radiation curing coating such as electron beam curing coatingor UV curing coating. The protective coating may comprise acrylate ormethacrylate polymers.

The protective coating may be applied prior or after pressing. In oneembodiment, the protective coating is applied on the second fibre mat 12prior to pressing, with an optional print thereon, and the first fibremat 11, the second fibre mat 12 are pressed together in one step.

The wood-based board 10, 10′, 10″ may be used as a building panel, forexample as floor panel, a wall panel, a furniture panel. The buildingpanel may be provided with a mechanical locking system for lockingbuilding panels to each other. The mechanical locking system may be ofthe type described in WO 2007/015669, WO 2008/004960, WO 2009/116926, orWO 2010/087752.

It is contemplated that there are numerous modifications of theembodiments described herein, which are still within the scope of thedisclosure. It is for example contemplated that more than one base layerof lignocellulosic particles may be provided, and that more than onesurface layer of cellulosic particles may be provided.

EXAMPLES

Example 1: Three different blends have been prepared. 750 g of a lowerbase layer comprising wood flour (200-600 μm) and 15%melamine-formaldehyde resin was scattered on a carrier to form a firstlayer of a first fibre mat. 2250 g of an upper base layer comprisingwood particles (2 cm in length, 0.5 cm in width) and 12%melamine-formaldehyde resin, was scattered on the first layer of thefirst fibre mat to form a second layer of the first fibre mat. Another750 g of a white surface layer comprising cellulosic fibres (150 μm) and15% melamine-formaldehyde resin, was scattered on top of the secondlayer of the first fibre mat to form a second fibre mat. The first fibremat and the second fibre mat were prepressed cold and moved into a hotpress, pressing with 180° C. in 135 seconds at 10 bar. The product was a900×700×8 mm particle board with a density of about 750 kg/m3 and aprintable white surface layer.

Example 2: A particle board in the dimension of 200×120×9 mm (density900 kg/m3) was formed by 41 g lower base layer, 120 g upper base layerand 41 g white surface layer. The lower base layer comprises wood flour(200-600 μm), 4% hydrophobing agent, 15% melamine-formaldehyde resin and2% hardener (calculated on the amount of resin). The upper base layercomprises wood particles (2 cm in length, 0.5 cm in width), 4%hydrophobing agent, 12% melamine-formaldehyde resin and 2% hardener(calculated on the amount of resin). The white surface layer comprisescellulosic particles (150 μm), 4% hydrophobing agent, 15%melamine-formaldehyde resin and 2% hardener (calculated on the amount ofresin). The layers have been scattered on a carrier to a first fibre matand a second fibre mat, prepressed cold and moved into a hot press. Thefirst and the second fibre mats were pressed in 180° C. for 100 secondsin an initial pressure of 40 bar for 5 seconds, a pressure of 5 barduring 85 seconds and finally a pressure of 10 bar for 10 seconds.

Embodiments

1. A method of manufacturing a wood-based board, comprising:

-   -   applying at least one first fibre mat, comprising a first mix        comprising lignocellulosic particles and a first binder, on a        carrier,    -   applying a second fibre mat, comprising a second mix comprising        cellulosic particles and a second binder, on said at least one        first fibre mat, and    -   pressing said at least one first fibre mat into a base layer and        the second fibre mat into a surface layer simultaneously,        thereby forming a wood-based board.

2. The method according to embodiment 1, wherein the step of pressingcomprises simultaneously adhering said base layer and the surface layerto each other.

3. The method according to embodiment 1, wherein the step of pressingsaid at least one fibre mat and the second fibre mat comprises applyingheat and pressure, and wherein pressure and/or binder content of thesecond fibre mat are chosen such that the surface layer remains opaqueafter curing.

4. The method according to embodiment 1, wherein pressing comprisescuring said at least one first fibre mat into a base layer and thesecond fibre mat into a surface layer simultaneously.

5. The method according to embodiment 1, further comprising printing aprint on the second fibre mat before pressing.

6. The method according to embodiment 1, further comprising printing aprint on the surface layer after pressing.

7. The method according to embodiment 1, wherein the carrier is aconveyor belt.

8. The method according to embodiment 1, further comprising applying aprotective layer on the surface layer.

9. The method according to embodiment 1, wherein the cellulosicparticles of the second mix are at least partially bleached.

10. The method according to embodiment 1, wherein the lignocellulosicparticles of the first mix are refined wood fibres, wood chips,unrefined wood fibres, wood strands, or saw dust.

11. The method according to embodiment 1, wherein the first binder is athermosetting resin.

12. The method according to embodiment 1, wherein the second binder is athermosetting resin.

13. The method according to embodiment 1, wherein the wood-based boardis a MDF or HDF.

14. The method according to embodiment 1, wherein the wood-based boardis a particle board or an oriented strand board.

15. A wood-based board, comprising

-   -   a base layer comprising lignocellulosic particles and a first        binder,    -   a surface layer comprising cellulosic particles and a second        binder, and    -   wherein the building panel comprises a portion wherein        cellulosic particles from the surface layer are mixed with        lignocellulosic particles from said base layer.

16. A wood-based board according to embodiment 15, wherein thewood-based board is a HDF or MDF.

17. A wood-based board according to embodiment 15, wherein thewood-based board is a particle board or an oriented strand board.

18. A wood-based board according to embodiment 15, wherein the firstbinder is a thermosetting binder.

19. A wood-based board according to embodiment 15, wherein the secondbinder is a thermosetting binder.

20. A method of manufacturing a wood-based board, comprising:

-   -   applying at least one first fibre mat comprising a first mix        comprising lignocellulosic particles and a first binder on a        carrier,    -   applying a surface layer comprising cellulosic particles on said        at least one first fibre mat prior to pressing the at least one        first fibre mat, and    -   pressing the surface layer to said at least one first fibre mat,        thereby adhering the surface layer to said at least one first        fibre mat and forming a wood-based board.

21. The method according to embodiment 20, wherein the surface layercomprises a sheet.

22. The method according to embodiment 20, wherein the surface layercomprises a second fibre mat comprising cellulosic particles and asecond binder.

23. The method according to embodiment 20, wherein pressing comprisescuring said at least one first fibre mat into a base layer.

24. The method according to embodiment 20, further comprising printing aprint on the surface layer before or after pressing.

25. The method according to embodiment 20, wherein the carrier is aconveyor belt.

26. The method according to embodiment 20, wherein the first binder is athermosetting binder.

The invention claimed is:
 1. A wood-based board, comprising a lower baselayer comprising lignocellulosic particles and a binder, an upper baselayer comprising lignocellulosic particles and a binder, a surface layercomprising cellulosic particles and a binder, wherein the upper baselayer is arranged between the lower base layer and the surface layer,wherein the particle size of the lignocellulosic particles in the lowerbase layer correspond to the particle size of the cellulosic particlesin the surface layer, and wherein the particle size of thelignocellulosic particles in the lower base layer differ from theparticle size of the lignocellulosic particles in the upper base layer.2. The wood-based board according to claim 1, wherein thelignocellulosic particles in the lower base layer, and the cellulosicparticles in the surface layer, have a length of less than 10 mm, awidth between 1-2 mm, and a thickness between 0.1-0.2 mm.
 3. Thewood-based board according to claim 1, wherein the particle size of thelignocellulosic particles in the upper base layer, exceeds the particlesize of the lignocellulosic particles in the lower baser layer and theparticle size of the cellulosic particles in the surface layer.
 4. Thewood-based board according to claim 3, wherein the lignocellulosicparticles in the upper base layer have a length between 12-20 mm, awidth of about 4 mm, and a thickness between 0.2-0.3 mm.
 5. Thewood-based board according to claim 1, wherein the wood-based board is ahigh density fibre or medium density fibre.
 6. The wood-based boardaccording to claim 1, wherein the wood-based board is a particle boardor an oriented strand board.
 7. The wood-based board according to claim1, wherein the binder is a thermosetting binder.
 8. The wood-based boardaccording to claim 1, wherein the binder in the lower base layer is thesame as the binder in the surface layer.